package murmur3

import (
    "hash"
)

// digest64 is half a digest128.
type digest64 digest128

// New64 returns a 64-bit hasher
func New64() hash.Hash64 {
    return New64WithSeed(0)
}

// New64WithSeed returns a 64-bit hasher set with explicit seed value
func New64WithSeed(seed uint32) hash.Hash64 {
    d := (*digest64)(New128WithSeed(seed).(*digest128))
    return d
}

func (d *digest64) Sum(in []byte) []byte {
    // Make a copy of d so that caller can keep writing and summing.
    d0 := *d
    hash := d0.checkSum()
    return append(in, hash[:]...)
}

func (d *digest64) checkSum() []byte {
    h1 := d.Sum64()
    return append([]byte{},
        byte(h1>>56), byte(h1>>48), byte(h1>>40), byte(h1>>32),
        byte(h1>>24), byte(h1>>16), byte(h1>>8), byte(h1))
}

func (d *digest64) Sum64() uint64 {
    h1, _ := (*digest128)(d).Sum128()
    return h1
}

// Sum64 returns the MurmurHash3 sum of data. It is equivalent to the
// following sequence (without the extra burden and the extra allocation):
//     hasher := New64()
//     hasher.Write(data)
//     return hasher.Sum64()
func Sum64(data []byte) uint64 {
    return Sum64WithSeed(data, 0)
}

// Sum64WithSeed returns the MurmurHash3 sum of data. It is equivalent to the
// following sequence (without the extra burden and the extra allocation):
//     hasher := New64WithSeed(seed)
//     hasher.Write(data)
//     return hasher.Sum64()
func Sum64WithSeed(data []byte, seed uint32) uint64 {
    d := &digest128{h1: uint64(seed), h2: uint64(seed)}
    d.seed = seed
    d.tail = d.bmix(data)
    d.clen = len(data)
    h1, _ := d.Sum128()
    return h1
}
